Time for a Change? Donald Trump Will Test a Forecasting Model

By Brendan Nyhan

May 10, 2016

With Donald Trump’s unfavorable ratings at record levels, the Republican Party’s prospects for taking back the White House already seem bleak. But its chances may be even worse yet. The doubts Mr. Trump has raised during his primary campaign also undermine the strongest rationale for any Republican candidate in this election: the need for new leadership after eight years of Democratic control of the White House.

The Emory University political scientist Alan Abramowitz highlights this factor in his “time for a change” forecasting model of presidential election outcomes. “When a party has held the White House for two or more terms,” he writes, “voters will be more likely to feel that it is time to give the opposing party an opportunity to govern than when a party has held the White House for only one term.”

Mr. Abramowitz finds that the party in power performs approximately five percentage points worse in the popular vote after two or more terms in office in a model that controls for the current president’s approval rating and the state of the economy. The sample size of post-World War II elections is very small, but Mr. Abramowitz’s model dominates the field in its forecastingaccuracy.

Both Mr. Abramowitz’s model and a similar one from the political scientists John Sides, Michael Tesler and Lynn Vavreck (an Upshot contributor) would characterize Republicans as the favorite in this election with an estimated probability of winning of approximately 60 percent. As Mr. Sides notes, the G.O.P. edge is due in large part “to the White House’s greater tendency to change hands the longer the incumbent party has been there.”

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Demonstrating against Donald Trump outside a campaign event in Charleston, W.Va., this month.CreditTy Wright for The New York Times

But these forecasts are made based on simple models that do not include any information about the nominees (and implicitly assume, as Mr. Abramowitz notes, that the parties select mainstream candidates). In contrast, betting and prediction markets that take the likely party nominees into account put Mr. Trump’s chances of winning in November at approximately 25 percent.

Why, then, is Mr. Trump looking so likely to underperform in November? Even his unfavorability ratings may not fully explain his diminished chances. Candidates who are initially not seen as personally likable can overcome those perceptions, as Bill Clinton did in 1992, another “time for a change” election (though Mr. Trump’s ratings are worse, and he has been known for longer at the national level).

For instance, consider a counterfactual situation in which Ted Cruz, Mr. Trump’s chief rival, became the nominee. Mr. Cruz also had high unfavorable numbers before dropping out of the race, but if he had won the G.O.P. nomination under normal circumstances, most Republicans would have probably rallied around him (as they did around Mitt Romney in 2012), and the electorate would have eventually come to see him somewhat less negatively.

In Mr. Trump’s case, his reputation for irresponsibility and lack of political experience overshadow the “time for a change” message. He frequently calls for new leadership — a message that would normally be the strongest G.O.P. appeal in an election year when the economy is not weak enough to be the focus of the opposition’s campaign. But instead of being a referendum on the incumbent party’s failures, this election seems likely to turn on how voters view Mr. Trump himself. Many voters who might have been open to an alternative after eight years of President Obama will instead ponder whether it is too risky to vote for Mr. Trump, especially after Mrs. Clinton makes his qualifications the central message of her campaign.

Mr. Trump could still win, but he will have to find some way to turn the focus back to Mrs. Clinton and the Democrats and to convince voters that the change in leadership he represents is desirable.

Correction:

An earlier version of this article gave the wrong election year that most Republicans rallied around Mitt Romney. It was 2012, not 2008.